The purpose of this research program is to conduct a prospective investigation of the biological correlates of social and emotional development during middle childhood and the beginning of puberty in African-American and White girls. Over the course of four years, 240 girls and their families from integrated, working and middle- class communities will be studied in order to examine the influence of individual and social factors on the psychological development of girls beginning in third and continuing through sixth grade. The goal of this project is to understand in what ways physiological processes and relation- ships with parents and peers set girls on various trajectories leading to more and less positive adjustment. Adjustment is defined in terms of three domains: emotional development, identity and self-concept, and school disengagement. The investigators' goal is to understand better the processes underlying development during middle childhood in order to add to the basic knowledge on development during this period as well as to identify the processes through which biological and contextual factors influence girls' adjustment and well-being during these years. Correlates of development to be considered are the onset of puberty, individual differences in responsivity to stress, family relationships and interactions, peer relationships, and identity and self-concepts. While biological and social interactions in development have been a focus of investigations of adolescence and infancy, little prospective research has focused on middle childhood; this is the age at which pubertal processes are initiated and at which peer relationships become more salient, and parental relationships may begin to change. The goal of this project is to understand in what ways physiological processes and relationships with parents and peers set girls on various trajectories leading to more and less positive adjustment. Adjustment is defined in terms of three domains: emotional development, identity and self-concept, and school disengagement. The project is designed to address six primary questions: (a) Do various indices of pubertal processes render girls at risk for problems in the three above mentioned domains? (b) Does high reactivity to potentially stressful situations amplify the potential effects of early pubertal development? (c) Do poor peer relationships prior to the onset of puberty intensify the effects of early development? (d) Do positive family relationships protect girls from the possible effects of early pubertal development or the effects of early puberty in conjunction with high reactivity? (e) Do life events, particularly those in family, influence pubertal timing? (f) Finally, are the associations among puberty, reactivity, and interpersonal relationships vis-a-vis adjustment similar or different for White and African-American girls? This final question is especially salient given the additional potential stressor of racial discrimination or rejection by peer groups based on racial membership that many minority girls are likely to experience.